Vision

 

Radios operating in the unlicensed ISM bands (e.g. 868 MHz, 915 MHz, 2.4 GHz) need to share their frequency band with a substantial number of other users. Due to the loose regulations and the non-regulated amount of users inherent to ISM bands, interference might be severe and the different interference scenarios are hard to predict.

Therefore one of the biggest challenges for unlicensed short-range radios is providing data transfer in a robust and reliable fashion.   

The main goal of this research is to come up with ultra-low power, short-range, low data rate radios enabling reliable communication in crowded ISM bands with power consumptions substantial below what is available today, in order to facilitate energy scavenging and a level of integration that allows operation with a minimum amount of external components (filter, crystals …)

Where we are and where we want to go

Architectures and designs of commercially available low power, low data rate, short-range radios are strongly driven by the quest for immunity to interferers. Consequently most of these radios make use of extensive filtering by employing bulky off-chip or power-hungry on-chip filters. Further, they often rely on high accurate reference frequencies almost always leading to an external crystal.

This research project tries to employ concepts recently developed for ultra-low power, highly integrated transmitter and receiver circuits (link to PicoRadio) together with principles of communication theory to come up with highly robust, ultra-low power, highly integrated solutions for the short range low data rate regime.

One idea is, instead of trying to make the radios resilient to interferers, to make them more intelligent so that they notice when their communication is jammed and switch to another band where no interferer is present (Sly Radios). Another opportunity might be frequency hopping in order to decrease the probability of interference.

First steps

In the course of the PicoRadio (link) project, various ultra-low power, short range, low data - rate radios based on high quality FBAR (Film Bulk Acoustic Resonators) oscillators where developed and have been proven to be superior in terms of power consumption and level of integration to other published radios with comparable performance.

The key to their low power performance is the high quality factor Q of the high-frequency FBARs, enabling low power oscillators with excellent phase noise and frequency stability operating directly at the RF. However, due to the high Q of the resonators, such oscillators are relatively hard to tune and offer only a limited frequency tuning range. Therefore those radios work on more or less fixed single frequencies.

Together with the modest frequency selectivity of the receivers, this makes them susceptible to close by interfere.

In order to make these receivers more robust without a need for increasing frequency selectivity, we focus on equipping them with the ability to switch to different frequency bands on the fly.

As a result of this, the current research is focusing on tunable high Q resonator based oscillators in the GHz frequency range. The target specifications for these oscillators include tuning ranges in the order of several 10s to 100s of MHz and a performance in terms of phase noise and power consumption comparable to the un-tuned oscillators.

Relevant Publications  

  • B. Otis, M. Sheets, Y. H. Chee, H. Qin, N. Pletcher, J. Rabaey, "Circuits and Technologies for Wireless Sensor Networks," chapter in: AmIware: Hardware Technology Drivers of Ambient Intelligence. Springer, 2006.
  • Y. H. Chee, A.M. Niknejad, J. Rabaey, "An Ultra-Low Power Injection Locked Transmitter for Wireless Sensor Networks," Proc. IEEE 2005 Custom Integrated Circuits Conference, pp. 797-800, Sep. 2005.
  • Y. H. Chee, A.M. Niknejad, J. Rabaey, "A Sub-100uW 1.9-GHz CMOS Oscillator Using FBAR Resonator," Dig. Papers, 2005 IEEE Radio Frequency Integrated Circuits Symp., pp. 123-126, Jun. 2005.
  • J. Rabaey, B. Otis, Y.H. Chee, R. Lu, N. Pletcher, S. Gambini, "Highly Integrated Ultra-Low Power RF Transceivers for Wireless Sensor Networks", chapter in Low-Power Electronic Design, edited by Christian Piguet, CRC Press, 2005.
  • B. Otis, Y.H. Chee, J. Rabaey, "A 400uW Rx, 1.6mW Tx Super-regenerative transceiver for wireless sensor networks," Proceedings of the IEEE ISSCC, Feb 2005.
  • B. Otis, Y.H. Chee, R. Lu, N.M. Pletcher, J.M. Rabaey, "An Ultra-Low Power MEMS-Based Two-Channel Transceiver for Wireless Sensor Networks," IEEE Symp. VLSI Circuits, June 2004.

Contact Information

For more information, contact Michael Mark (markm_at_eecs.berkeley.edu)